If user profile doesn't contain language setting, default to his Google account settings.

chrome/browser/profiles/profile_impl.cc

Index: chrome/browser/profiles/profile_impl.cc
diff --git a/chrome/browser/profiles/profile_impl.cc b/chrome/browser/profiles/profile_impl.cc
index c3650e8ba514879259e8d40b907acc558da8e9aa..720a4007425132e0205c1aee10d3721e5247b43b 100644
--- a/chrome/browser/profiles/profile_impl.cc
+++ b/chrome/browser/profiles/profile_impl.cc
@@ -8,6 +8,7 @@
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
+#include "base/debug/stack_trace.h"

[sail, 2013/09/09 22:02:17]

don't need?

 #include "base/debug/trace_event.h"
 #include "base/environment.h"
 #include "base/file_util.h"
@@ -29,6 +30,7 @@
 #include "chrome/browser/bookmarks/bookmark_model_factory.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/chrome_notification_types.h"
+#include "chrome/browser/chromeos/login/language_switch_menu.h"

[sail, 2013/09/09 22:02:17]

don't need?

 #include "chrome/browser/content_settings/cookie_settings.h"
 #include "chrome/browser/content_settings/host_content_settings_map.h"
 #include "chrome/browser/download/chrome_download_manager_delegate.h"
@@ -1042,7 +1044,9 @@ void ProfileImpl::ChangeAppLocale(
         // (2) on next login we assume that synchronization is already completed
         //     and we may finalize initialization.
         GetPrefs()->SetString(prefs::kApplicationLocaleBackup, cur_locale);
-        if (!backup_locale.empty())
+        if (!new_locale.empty())
+          GetPrefs()->SetString(prefs::kApplicationLocale, new_locale);
+        else if (!backup_locale.empty())
           GetPrefs()->SetString(prefs::kApplicationLocale, backup_locale);
         do_update_pref = false;
       }